Childhood is an extremely sensitive period in human development, during which the brain, especially the circuitry governing emotion, attention, self-control, and stress, is shaped by the interplay of the child's genes and experiences. One of the unfortunate experiences that marks many childhoods is bullying. Bullying is a global social phenomenon that has existed in neighborhoods and schools for centuries and is still rising today. Bullying is defined as aggressive behavior that is persistent, intentional, and involves an imbalance of power or strength. It usually targets children and teenagers due to their lack of empathy, which is the capacity to understand or feel what another being is experiencing from within the other being's frame of reference, or the capacity to place oneself in another's position. Bullying can occur as verbal, physical, relational, or cyber-bullying.
The main roles identified in bullying includes the bully, the victim, and the bystander, with a negative impact on everyone involved. In particular, for the bullies, the consequences vary from violent behavior and anti-social personality disorder to educational problems, while the victims face anxiety, depression, lower self-confidence, and even self-harmful tendencies. The bystander tends to feel fearful and powerless to act, and guilty for not acting. One problem with bullying is the distinction in these roles—bully, victim, bystander—since a child may have multiple roles at various times. For example, a child may be the one subjected to bullying in one situation, while being the bully in another setting, depending on the social surroundings, which increases the difficulty in realizing effective intervention.